The solution is actually quite simple and simply involves you using an image for the marker icons. As part of Google Chart Tools you can generate markers that contain a letter or number, as well change the marker and font colors.

Here are custom icons with the updated “visual refresh” style that you can generate quickly via a simple .vbs script. I also included a large pre-generated set that you can use immediately with multiple color options: https://github.com/Concept211/Google-Maps-Markers